Process for forming composite material by electrodeposition under the influence of a centrifugal force field

ABSTRACT

An improvement in the techniques of forming composite material by electrodeposition whereby the electrolyte slurry containing the reinforcing whiskers or fibers is subjected to a centrifugal force field to press the whiskers or fibers against the cathode and form a permeable mat thereagainst for encapsulation by the deposited matrix metal. Thus, the percent by volume of the whiskers or fibers in the deposited composite material can be increased substantially above that which is possible by conventional electrodeposition technique.

nited States Patent 91 Ahmad [4 1 Feb. 13,1973

[54] PROCESS FOR FORMING COMPOSITE MATERIAL BY ELECTRODEPOSITION UNDER THE INFLUENCE OF A CENTRIFUGAL FORCE FIELD [75] Inventor: Iqbal Ahmad, Elnora, NY.

[73] Assignee: The United States of America as represented by the Secretary of the Army [22] Filed: May 13, 1969 [21] Appl. No.: 824,129

[52] US. Cl. ..204/16, 204/9, 204/26, 204/212, 204/281 [51] Int. Cl ..C23b 5/48, C23b 7/02, C23b 5/68 [58] Field of Search ..204/38 R, 38 B, 181, 26, 16, 204/199, 9; 117/101 [56] References Cited UNITED STATES PATENTS Benner et al. ..204/16 T0 POWER SOURCE 3 ,06 l ,525 10/ l 962 Grazen ..204/16 2,721,837 10/1955 Backer ..204/16 3,591,466 7/ 1971 Heiman ..204/9 FOREIGN PATENTS OR APPLICATIONS 546,465 3/1932 Germany ..204/2 1 3 Primary ExaminerJohn H. Mack Assistant Examiner-R. L. Andrews AttorneyI-larry M. Saragovitz, Edward J. Kelly, Herbert Berl and Albert E. Arnold, Jr.

[57] ABSTRACT 9 Claims, 5 Drawing Figures PATENTEBFEBI 3 191a SHEET 10F 3 Big:

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INVENTOR lqPul Ahmui BY M wiamu PATENTED FEB] 3:913

SHEET 30F 3 AI msmus PROCESS FOR FORMING COMPOSITE MATERIAL BY ELECTRODEPOSITION UNDER THE INFLUENCE OF A CENTRIFUGAL FORCE FIELD The invention described herein may be manufactured, used, and licensed by or for the Government for governmental purposes without the payment to me of any royalty thereon.

BACKGROUND OF THE INVENTION This invention is related to the art of forming composite material through the addition of reinforcing particles to a matrix to improve the properties thereof, and pertains more particularly to the technique of forming these composite materials by electro-deposition.

The phenomenal progress in space science and technology and the developments in weaponry and logistics during the past two decades have created a pressing demand for materials which have a high strength and modulus-to-density ratio, and high-temperature capability. As a result, a large number of super alloys have been developed. These, however, still fall short of some of the rigorous requirements of the advanced engineering concepts.

The success achieved in reinforcing plastics with glass filaments and the availability in recent years of high strength and high temperature metallic and ceramic fibers and especially single crystals, now known in the art as whiskers, have initiated great activity in their utilization for reinforcement of weaker metallic matrices to produce high temperature, high strength and light weight composite materials. Theoretically, for instance, nickel with 50 volume percent alpha Al- O whiskers will be superior to any of the available high temperature super alloys.

A number of techniques are being explored for the fabrication of these reinforced metal composites. One of these techniques showing considerable promise is that of electrodeposition because in this technique the reinforcing particles such as whiskers, refractory powder or fibers are not subjected to damaging pressures or heat as they are suspended in an electrolyte and arecodeposited with the matrix metal at relatively low temperatures and at atmosphere pressure. This technique, however; has limitations as the maximum content of the dispersoids in the matrix is limited to approximately l volume percent by the density of the slurry.

SUMMARY OF THE INVENTION It is a principal object of this invention to provide an improvement in the technique of producing composite material by electro-deposition whereby a greater volume percent of reinforcing particles can be added to the composite material than has been possible before by this technique.

It is another object of this invention to produce composite material by electrodeposition under the influence of a centrifugal force field so as to increase the volume percent, of the reinforcing particles in the material.

It is another and still further object of this invention to provide a process for producing composite material by electro-deposition under the'influence of a centrifugal force field in which the volume percent of the reinforcing particles is controlled by the amount thereof in the electrolyte, the magnitude of the centrifugal force field and the densities of the slurry and the electrolytic current.

It is still another object of this invention to provide a process for producing composite material by electrodeposition under the influence of a centrifugal force field so that the resulting material is sound, imporous and has a large volume percent of reinforcing particles.

It is a further object of this invention to produce by electro-deposition an aluminum oxide whisker-nickel composite in which the volume percent of aluminum oxide whiskers is greater than 15 percent.

Further objects and advantages of the invention will be apparent from the following specification and the accompanying drawings which are for the purpose of illustration only.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of an apparatus which can be used in the process of this invention for forming composite material by electrodeposition under the influence of a centrifugal force field;

FIG. 2 is an enlarged view taken along line 2-2 of FIG. 1;

FIG. 3 is a view taken along line 3-3 of FIG. 2 showing the slurry subjected to the centrifugal force field and displaced thereby upwardly along the wall of the rotating cell and between the anode and cathode;

FIG. 4 is a reduced view similar to FIG. 2 but shows an alternate embodiment in which the apparatus is adapted for plating the composite material on the inside of a cylinder; and

FIG. 5 is an enlarged view taken along line 5-5 of FIG. 4.

DESCRIPTION OF PREFERRED EMBODIMENTS Shown in FIGS. 1-3 is an electrolytic apparatus 12 for depositing a composite material as arcuate strips from a slurry 14 by electro-deposition under the influence of a centrifugal force field CF. Apparatus 12 comprises a centrifuge 15 having a cylindrical housing 16 and a cell 18 therein. Cell 18 is rotated by a high speed motor 21 to produce centrifugal force field CF.

The rate of rotation, and therefore the magnitude of centrifugal force field CF, is controlled by rheostat means 22 which is operationally disposed between motor 21 and a source of power not shown.

Shaft 24 of motor 21, to which cell 18 is mounted for rotation, extends axially into the cell and a disc 26 is mounted to such extending end 27 by means of an insulating connector 25 for simultaneous rotation therewith. Disc 26 is formed from copper as it is an excellent conductor of electricity, and is provided with an axial hub 29 having a well 30 extending downwardly thereinto to receive mercury pool 32. Disc 26 carries three nickel anodes 34 which are disposed apart, as shown in FIG. 2, and parallel to the axis of shaft and to the vertical wall 44 of cell 18. Anodes 34 are also mounted to disc 26, as noted at 36, so as to be radially adjustable, respective to disc 26.

Mounted to the inside of wall 44 of cell 18 so as to be electrically insulated therefrom are three cathodes 46 which are disposed in radial alignment with anodes 34 and concentric therewith. A collector ring 50 is mounted to the inside of housing 16 and electrical connection is made between each cathode 46 and such ring by means of a carbon brush 52 which is displaceably mounted in a mount 53 so as to be spring-pressed against the ring. Each cathode 46 is provided with a cylindrical boss 55 which extends through a hole in wall 44, and mount 53 is threadingly engaged with the boss to provide electrical connection between carbon brush 52 and the cathode and also firmly hold the cathode to the wall. Mounts 43 and bosses 55 are, of course, insulated from wall 44.

DC current is supplied to anodes 34 and cathodes 46 from a source of power (not shown) through a regulator 54 which is adapted for adjusting the voltage and current density output therefrom. Positive lead 56 from regulator 54 terminates in mercury pool 32 so as to apply a positive potential to anodes 34, through disc 26, during rotation of cell 18. Negative lead 58 from regulator 54 is connected to ring 50 so as to apply a negative potential to cathodes 46 through carbon brushes 52.

Shown in FIGS. 4 and is another embodiment of apparatus 12 wherein 80 is adapted for plating the inside of a cylinder 82. In this embodiment, top 84 of cell 80 is threadingly mounted on wall 86 thereof to permit removal therefrom for insertion of cylinder 82 into the cell. Before cylinder 82 is inserted, a gasket 88 is installed in the bottom of cell 80 and after the cylinder is placed on top of such gasket another gasket 90 is placed on top of the cylinder. When top 84 is installed on wall 86 and tightened, a seal is made between cylinder 82 and gaskets 88 and 90 to form a reservoir for slurry 14 when poured thereinto through opening 92 in top 84.

Electrical connection is made between negative lead 58 and cylinder 82, so that it will be made cathodic when current is applied thereto, by means of ring 50 and at least three carbon brushes 52 and mounts S3 therefor as described in the basic embodiment. In addition, provided for each mount 53 is a bushing 94 with an external flange 96, which is mounted through a hole in wall 86 so as to be insulated therefrom and so that the flange is located on the inside of the wall. Each bushing 94 is provided with a threaded central bore 98 which is counterbored at 100 to slidingly receive a pad 102. Threaded portion 103 of mount 53 is received by bore 98 so as to act against pad 102, when tightened, to press the pad against the side of cylinder 82. Together, bushings 94 cooperate, when tightened, to center cylinder 82 in cell 80, hold the cylinder against displacement, and provide electrical contact therewith.

Anodes 104 are substantially similar to anodes 34 and, as shown in FIGS. 4 and 5, sufficient space must be left between the top and bottom of anodes 104 and therebetween to permit the flow of slurry l4 therethrough.

Apparatus 12 is utilized to form strips of aluminum oxide whisker-nickel composite material by the process which comprises the steps of forming slurry 14 by mixing a predetermined amount of aluminum oxide whiskers, as explained later, in an electrolyte. A suitable electrolyte which has been used to advantage is a sulphamate bath which comprises:

Nickel sulphamate 43 oz/gal Nickel as metal l0 oz/gal Boric Acid 3/4 oz/gal Nickel Bromide (cone) 7 oz/gal Diluted to a specific gravity of 29-3 1 (Baume scale).

Cell 18 is energized for rotation at a predetermined speed by rheostat means 22 and slurry 14 is thoroughly mixed to distribute the aluminum oxide whiskers evenly therein. Slurry 14, while still thoroughly mixed, is poured into cell 18 and immediately, through centrifugal force field CF created by the rotation'thereof, the slurry rises along wall 44 and between the facing surfaces of anodes 34 and cathodes 46, as shown in FIG. 3, to provide electrical communication therebetween. Through the influence of centrifugal force field CF the aluminum oxide whiskers are moved through the electrolyte against cathodes 46 to form a permeable mat thereagainst. The degree of compactness of the matted whiskers is determined by the magnitude of centrifugal force field CF and therefore this is one of the factors which determines the volume percent of the whiskers in the deposited composite because the greater the whiskers are compacted together the greater will be their volume percent in the resulting composite. It is, however, important that the magnitude of centrifugal force CF is not so great that the whiskers form an impermeable mat against cathodes 46. If this should happen, the distributing ions would be prevented from penetrating the mat and encapsulating the whiskers therein.

Other factors which control the volume percent of the whiskers, and must be considered in determining the amount thereof to be added to the electrolyte in slurry 14, are the densities of the slurry, and the current applied to anodes 34 and cathodes 46. The latter is particularly important because when the current density is low the distributing ions passing to cathodes 46 from anodes 34 pass freely through the matted whiskers to completely encapsulate the whiskers from the inside of the mat out and thereby form a solid, void-free mass. When the current density is too high the depositing ions could form bridges between the whiskers and so create voids in the mass.

When the deposit is formed to the desired thickness the current is shut off, motor 21 is deenergized and cathodes 46 removed from cell 18. The deposited composite is then stripped from each of cathodes 46.

In a laboratory set-up wherein cell 18 was 5 inches in diameter, 8 grams of alpha-A1 0 whiskers were added to cc of the sulphamate electrolyte, thoroughly mixed by an electrosonic probe and poured into the cell which was rotating at 1,600 rpm. A 3-volt potential and 26 amp/sq. ft. current density was then applied to anodes 34 and cathodes 46. This resulted in a deposited strip of composite material on each cathode which was 4 inches long, one-half inch wide and 0.0.60 inch thick and having a l6.8 volume percent of aluminum oxide whiskers. The highest volume percent of aluminum oxide whiskers which could be obtained without the utilization of centrifugal force was 10 volume percent.

It is obvious that other metals can be used in this same process as the matrix for a composite material. It is also obvious that particles of other refractory materials can be used as reinforcements. Also, that combinations of these particles from different refractory materials can be used to achieve a composite material with improved properties in different fields.

The same process described above can be also used to form a plating on the inside wall of a cylinder as illustrated in FIGS. 4 and 5.

I wish it to be understood that I do not desire to be limited to the exact details of construction shown and described, for obvious modifications will occur to a person skilled in the art.

I claim:

1. The process of producing by electrodeposition a composite material including a metallic matrix and reinforcing particles, comprising the steps of:

mounting metal collecting cathode means in a rotatable cell concentrically around the outside of anode means radially spaced therefrom; mixing a predetermined amount of the reinforcing particles in a liquid electrolyte to form a slurry; placing said mixed slurry into the space between said cathode means and said anode means;

rotating said cathode means, anode means, and slurry simultaneously at a speed sufficient to form and hold a permeable mat of said reinforcing particles against said cathode means by centrifugal force; and

applying an electric current to said anode means and said cathode means while rotating said cathode means, anode means, and said slurry to produce a deposit of said composite material on said cathode means by electrodeposition.

2. The process as defined in claim 1 and including the step of adjusting the speed of the rotation of the cell so as to create a centrifugal force field of sufficient magnitude to produce a desired volume percent of the reinforcing particles in the composite material.

3. The process as defined in claim 1 and including the step of adjusting the current density applied to the anode and the cathode means below that which would cause bridging and the creation of voids in the composite material.

4. The process as defined in claim 1 and including the step of adding particles of more than one reinforcing material to the slurry to improve different properties of the matrix metal.

5. The process as defined in claim 1 wherein the reinforcing particles are in the form of whiskers, fibers or discontinuous filaments.

6. The process as defined in claim 1 wherein the cathode means is in the configuration of a cylinder and the deposited composite material is formed on the inside thereof as a surface plating.

7. The process as defined in claim 1 wherein said cathode means comprises a plurality of arcuate cathodes.

8. The process as defined in claim 1 and including the steps of removing said cathode means after sufficient electrodeposition of composite material, and stripping the collected composite material from said cathode means.

9. The process as defined in claim 1 wherein said composite material is an aluminum oxide whiskers and nickel composite. 

1. The process of producing by electrodeposition a composite material including a metallic matrix and reinforcing particles, comprising the steps of: mounting metal collecting cathode means in a rotatable cell concentrically around the outside of anode means radially spaced therefrom; mixing a predetermined amount of the reinforcing particles in a liquid electrolyte to form a slurry; placing said mixed slurry into the space between said cathode means and said anode means; rotating said cathode means, anode means, and slurry simultaneously at a speed sufficient to form and hold a permeable mat of said reinforcing particles against said cathode means by centrifugal force; and applying an electric current to said anode means and said cathode means while rotating said cathode means, anode means, and said slurry to produce a deposit of said composite material on said cathode means by electrodeposition.
 2. The process as defined in claim 1 and including the step of adjusting the speed of the rotation of the cell so as to create a centrifugal force field of sufficient magnitude to produce a desired volume percent of the reinforcing particles in the composite material.
 3. The process as defined in claim 1 and including the step of adjusting the current density applied to the anode and the cathode means below thAt which would cause bridging and the creation of voids in the composite material.
 4. The process as defined in claim 1 and including the step of adding particles of more than one reinforcing material to the slurry to improve different properties of the matrix metal.
 5. The process as defined in claim 1 wherein the reinforcing particles are in the form of whiskers, fibers or discontinuous filaments.
 6. The process as defined in claim 1 wherein the cathode means is in the configuration of a cylinder and the deposited composite material is formed on the inside thereof as a surface plating.
 7. The process as defined in claim 1 wherein said cathode means comprises a plurality of arcuate cathodes.
 8. The process as defined in claim 1 and including the steps of removing said cathode means after sufficient electrodeposition of composite material, and stripping the collected composite material from said cathode means. 